Semiconductor device having contact plug and method for manufacturing the same

ABSTRACT

A semiconductor device having a contact plug and a method for manufacturing the same are provided. A diffusion barrier layer is formed on a semiconductor substrate on which an insulating layer having a contact hole has been formed. A first metal layer is formed on the diffusion barrier layer filling the contact hole, and the first metal layer is etched back to a predetermined depth to expose a void in the first metal layer, if any, thereby forming a first sub-plug. A second metal layer is formed on the semiconductor substrate on which the first sub-plug has been formed. The second metal layer is polished so as to expose the top surface of the diffusion barrier layer on the insulating layer. As a result, a second sub-plug in the contact hole is formed. Therefore, a contact plug comprising the first and second sub-plugs and having strong resistance to particles generated in chemical and mechanical polishing (CMP) has been formed in the contact hole without a void or crack.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device, and moreparticularly, to a semiconductor device having a contact plug and amethod for manufacturing the same.

[0003] 2. Description of the Related Art

[0004] A contact plug formed within an insulating layer between asemiconductor substrate and a bit line or a storage electrode has beenused for connecting an active region on the semiconductor substrate andthe bit line, for connecting an active region on a semiconductorsubstrate and a storage electrode of a capacitor, and for connecting anactive region of a peripheral circuit or a gate electrode and a bitline. There are two different types of techniques for forming a contactplug, one technique using tungsten and the other technique usingtitanium nitride. In the case of using tungsten having a strong tensilestrength to form a contact plug, a void may be formed in the contacthole. In addition, after the contact hole is filled with tungsten,chemical mechanical polishing (CMP) and cleaning processes are performedto complete the formation of a contact plug. At this time, tungsten maybe melted or dissolved by a cleaner used in the cleaning process. Thus,particles generated in the chemical mechanical polishing process may notbe completely removed in the cleaning process.

[0005] On the other hand, a titanium nitride layer has superior stepcoverage compared with tungsten and thus, a void can be prevented in acontact plug made of titanium nitride. Also, the problem occurring in acontact plug made of tungsten where tungsten is melted or dissolved by acleaner in the cleaning process is not observed in a contact plug madeof titanium nitride. For this reason, it is possible to sufficientlyremove particles generated in a chemical mechanical polishing process byintensively performing a cleaning process. In addition, in the case offorming a contact plug of titanium nitride, an adhesive layer used forenhancing adhesive strength between tungsten and an insulating layercontaining a silicon component, that is, a titanium nitride layer is notrequired in depositing a tungsten bit line in contact with the contactplug because the titanium nitride layer used in the formation of thecontact plug can act as an adhesive layer. Thus, the thickness of a bitline structure including a bit line and an adhesive layer can bereduced. Therefore, it is possible to prevent the process of etchingback the bit line structure from being excessively performed, therebyminimizing the degree by which an diffusion barrier layer formed in thecontact plug is recessed. However, if the titanium nitride layer isdeposited to a thickness of 1000 Å or greater, cracks may occur in thecontact plug due to stress.

SUMMARY OF THE INVENTION

[0006] To solve the above problems, the present invention provides asemiconductor device including a contact plug that has substantially novoid or crack and a method for manufacturing the same.

[0007] Also, the present invention provides a semiconductor deviceincluding a contact plug which has no void or crack and has strongresistance to particles generated in chemical and mechanical polishingand a method for manufacturing the same.

[0008] Accordingly, a semiconductor device in accordance with oneembodiment of the present invention includes a semiconductor substrate;an insulating layer formed on the semiconductor substrate and having acontact hole; an diffusion barrier layer formed on the insulating layerand the contact hole; and a contact plug which comprises a firstsub-plug filling the contact hole and formed to have a first heightrelative to the bottom of the contact hole and a second sub-plug formedto extend from the top surface of the first sub-plug to the top of thecontact hole.

[0009] The first sub-plug is formed of tungsten and the second sub-plugis formed of one of a titanium nitride layer and tungsten. In the caseof forming the second sub-plug of a titanium nitride layer, it ispreferable that the titanium nitride layer has a thickness no greaterthan 1000 Å, particularly, about 500 Å. The diffusion barrier layer isformed of titanium/titanium nitride.

[0010] In accordance with another embodiment of the present invention, amethod for manufacturing a semiconductor device includes preparing asemiconductor substrate; forming an insulating layer having a contacthole on the semiconductor substrate; forming an diffusion barrier layeron the insulating layer and the contact hole; and forming a plug in thecontact hole by forming a first sub-plug with a first height relativethe bottom of the contact hole and forming a second sub-plug extendingfrom the top surface of the first sub-plug to the top of the contacthole.

[0011] In an example method for forming a first sub-plug, a first metallayer is formed on the insulating layer having the contact hole and isetched back to a predetermined depth to which a void which may be formedin the first metal layer reaches. The first sub-plug is formed oftungsten. In an example method for forming a second sub-plug, a secondmetal layer is formed on the semiconductor substrate on which the firstsub-plug has been formed and is polished so as to expose the top surfaceof the diffusion barrier layer. The second sub-plug is formed of one oftungsten and a titanium nitride layer. The second sub-plug has athickness no greater than 1000 Å.

[0012] In accordance with one aspect of the present invention, asemiconductor device comprises a semiconductor substrate; an insulatinglayer formed on the semiconductor substrate and having a contact holetherethrough; a diffusion barrier layer formed on a surface of theinsulating layer and on surfaces within the contact hole; and a contactplug which comprises a first sub-plug that fills a lower portion of thecontact hole and a second sub-plug that fills an upper portion of thecontact hole on the first sub-plug.

[0013] In accordance with another aspect of the present invention, amethod for manufacturing a semiconductor device comprises forming aninsulating layer having a contact hole therethrough on a semiconductorsubstrate; forming a diffusion barrier layer on a surface of theinsulating layer and on surfaces within the contact hole; and forming aplug in the contact hole by forming a first sub-plug that fills a lowerportion of the contact hole and forming a second sub-plug that fills anupper portion of the contact hole on the first sub-plug.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above objects and advantages of the present invention willbecome more apparent by describing in detail a preferred embodimentthereof with reference to the attached drawings in which:

[0015]FIGS. 1 through 4 are cross-sectional diagrams illustrating amethod for manufacturing a contact plug according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention now will be described more fully withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown.

[0017] Referring to the embodiment shown in FIG. 1, an insulating layer12 is formed on a semiconductor substrate 10. A contact hole is formedby etching a predetermined portion of the insulating layer 12 to exposea region of an active region of the semiconductor substrate 10. Adiffusion barrier layer 14 is formed on the insulating layer 12 and atthe sidewalls and bottom surface of the contact hole. The diffusionbarrier layer 14 comprises a titanium/titanium nitride layer 14. Next, afirst metal layer 16, that is, a tungsten layer is formed on thediffusion barrier layer 14 filling the contact hole. A void 18 is formedin the first metal layer 16 filled in the contact hole. Here, the firstmetal layer 16 is a tungsten layer; however, any metal layer capable ofgenerating a void in the contact hole may be used as the first metallayer 16 instead of the tungsten layer.

[0018] Referring to FIG. 2, the first metal layer 16 is etched back to apredetermined depth to which the void 18 of FIG. 1 reaches, therebyforming a first sub-plug having a first height relative to the bottom ofthe contact hole.

[0019] Referring to FIG. 3, a second metal layer 22 is formed by atomiclayer deposition on the semiconductor substrate 10 on which the firstsub-plug 20 has been formed. Any material that resists melting ordissolving in a chemical mechanical polishing or cleaning process can beused as the second metal layer 22. The material of the second metallayer 22 may be the same as or different from the first metal layer 16.Specifically, the second metal layer 22 may be a tungsten or titaniumnitride layer. In the case of using a titanium nitride layer as thesecond metal layer 22, a cleaning process performed after the formationof a second sub-plug 24 can be intensively performed and thus, thesecond sub-plug can have strong resistance to particles generated inchemical mechanical polishing. In addition, in the case of using atitanium nitride layer as the second sub-plug 24, the second sub-plug ispreferably deposited to a thickness of no greater than 1000 Å,specifically, a thickness of about 500 Å.

[0020] Referring to FIG. 4, the second sub-plug 24 is formed byperforming a planarization process such as chemical mechanical polishing(CMP) on the second metal layer 22 of FIG. 3 so as to expose the topsurface of the diffusion barrier layer 14. As a result, a contact plugcomprising the first and second sub-plugs 20 and 24 has been formed inthe contact hole.

[0021] The first metal layer 16 is etched back to a predetermined depthto which the void 18 reaches and thus, there is no void in the firstsub-plug 20. If a material, which a cleaner used in a cleaning processsubsequent to a chemical mechanical polishing process has difficultymelting, is used as the second metal layer 22, the cleaning process canbe intensively performed. Therefore, it is possible to form a contactplug having strong resistance to particles generated in the chemicalmechanical polishing process for formation of the contact plug. In thepresent invention, a titanium nitride layer is used for producing theseeffects. The upper part of the contact plug is formed of a titaniumnitride layer, thereby minimizing the amount of time required in etchinga bit line to be formed at the upper part of the contact plug andminimizing the degree by which the diffusion barrier layer within thecontact hole is recessed.

[0022] While this invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor substrate; an insulating layer formed on the semiconductorsubstrate and having a contact hole therethrough; a diffusion barrierlayer formed on a surface of the insulating layer and on surfaces withinthe contact hole; and a contact plug which comprises a first sub-plugthat fills a lower portion of the contact hole and a second sub-plugthat fills an upper portion of the contact hole on the first sub-plug.2. The semiconductor device of claim 1, wherein the first sub-plug isformed of tungsten and the second sub-plug is formed of titaniumnitride.
 3. The semiconductor device of claim 2, wherein the titaniumnitride is formed to a thickness of no greater than approximately 1000Å.
 4. The semiconductor device of claim 2, wherein the diffusion barrierlayer is formed of titanium/titanium nitride.
 5. A method formanufacturing a semiconductor device comprising: forming an insulatinglayer having a contact hole therethrough on a semiconductor substrate;forming a diffusion barrier layer on a surface of the insulating layerand on surfaces within the contact hole; and forming a plug in thecontact hole by forming a first sub-plug that fills a lower portion ofthe contact hole and forming a second sub-plug that fills an upperportion of the contact hole on the first sub-plug.
 6. The method formanufacturing a semiconductor device of claim 5, wherein forming a firstsub-plug comprises forming a first metal layer on the insulating layerhaving the contact hole therethrough and etching back the first metallayer to a predetermined depth to expose a void in the first metallayer, if any.
 7. The method for manufacturing a semiconductor device ofclaim 5, wherein forming a second sub-plug comprises forming a secondmetal layer on the semiconductor substrate on which the first sub-plughas been formed and polishing the second metal layer so as to expose atop surface of the diffusion barrier layer on the insulating layer. 8.The method for manufacturing a semiconductor device of claim 6, whereinforming a second sub-plug comprises forming a second metal layer on thesemiconductor substrate on which the first sub-plug has been formed andpolishing the second metal layer so as to expose a top surface of thediffusion barrier layer on the insulating layer.
 9. The method formanufacturing a semiconductor device of claim 5, wherein the firstsub-plug is formed of tungsten.
 10. The method for manufacturing asemiconductor device of claim 5, wherein the second sub-plug is formedof one of tungsten and titanium nitride.
 11. The method formanufacturing a semiconductor device of claim 5, wherein the secondsub-plug is formed to a thickness no greater than 1000 Å.
 12. The methodfor manufacturing a semiconductor device of claim 5, wherein thediffusion barrier layer is formed of titanium/titanium nitride.